Circuit for aiding the collapse of an electromagnetic field

ABSTRACT

A circuit means is disclosed for aiding the collapse of an electromagnetic field in order to remove energy stored therein and thus to hasten movement of a movable member whose position is controlled by the strength of the electromagnetic field. In particular, an electronic device is used to provide a repeatable, uniform, rapid, controlled energy dissipating circuit path. By dissipating the energy stored in the electromagnetic field through a zener diode, uniformity of field collapse is assured, good repeatability is provided and actuation frequency of the field is increased.

United States Patent Nagy 51 May 30, 1972 s41 CIRCUIT FOR AIDING THE COLLAPSE 3,414,776 12/1968 Draayer ..3l7/l48.5 x OF AN ELECTROMAGNETIC FIELD 3,435,295 3/1969 Ladd, Jr. et al. ..317/14s.s x

[72] Inventor: John R. Nagy, Detroit, Mich. Primary Examinepiaurence M. Goodridse [73] Assignee: The Bendix Corporation Attorney-Robert A. Benziger and Flame, Hartz, Smith and h 22 Filed: Sept. 21, 1970 T [2]] Appl. No.: 74,057 [57] ABSTRACT A circuit means is disclosed for aiding the collapse of an elec- 52} US. Cl. 123/32 EA, 123/1 19, 123/139 E, tromagnetic field in order to-remove energy stored therein and 123/140 MC thus to hasten movement of a movable member whose posi- [51] Int. Cl ..F02m 51/00 on is Conn-cued by the strength f the electromagnetic Gen [58] Field of Search ..l23/32 EA, 1 19; 317/1485, In particular, an electronic d i e is used to provide a repeata- 317/DIG' 6 ble, uniform, rapid, controlled energy dissipating circuit path. By dissipating the energy stored in the electromagnetic field [56] References Cited through a zener diode, uniformity of field collapse is assured, UNITED STATES PATENTS good repeatability is provided and actuation frequency of the field is increased. 3,522,794 8/1970 Reichardt ..l23/l 19 X 3,41 1,045 11/1968 Reyner ..3 17/1485 2 Claim, 5 Drawing Figures Patented May 30,1972 3,665,899

3 Sheets-Sheet 1 I N VEN TOR WITNESS: BY jDfi/L 22692- 575242;; MAW

ATTORNEY Patented May 30, 1912 3,665,899

3 Sheets-Sheet 2 INVEN7 UR.

. 6v BY jam X27211 ATTOR IVE Y Patented May 30, 1972 3 Sheets-Sheet 5 MW J w 3 Pm m iga ..i|!.m+\! mm y MM d i mizmmq F COEFG ATTORNEY WITNESS CIRCUIT FOR AIDING COLLAPSE OF AN ELECTROMAGNETIC FIELD BACKGROUND OF THE INVENTION I. Field of the Invention The present invention relates to improvements in control circuitry for electromagnetic devices and, in particular, to circuits for providing rapid, uniform dissipation of energy from such electromagnetic devices as may be utilized in the injector valve means for electronic fuel control systems.

2. Background of the Invention In the field of electronic fuel control systems, it is well known to provide a main electrical or electronic computing circuit to generate electrical'pulses of variable duration for ultimate control of an electromagnetic injector valve means. The injector valve means is connected to a source of pressurized fuel and is adapted to pass a stream of fuel to the associated engine when opened in response to the main computing means variable duration pulses. Thus, the total amount of fuel injected for each actuation of the injector valve means is a function of the duration of the injector valve means open time.

With the application of electronic fuel control systems to reciprocating piston internal combustion engines for automotive uses, the total available injector valve means open time at high speed operation becomes a limiting operating factor with regard to total fuel injected. Thus, in order to maximize the quantity of fuel injected while the total available injector valve means open time is minimized, it becomes essential that the electromagnetic injector valve means be opened and closed as rapidly as possible so that the injector valve means will be wide open for amaximum percentage of the time available for injection. The main electronic computing circuit is readily adaptable to produce control pulses having nearly vertical leading and trailing and the capability of the electromagnetic injector valve means to respond to, or follow, the control pulse thus becomes the limiting factor. Rapid valve opening time can be obtained by optimum design of the injector valve means coupled with electronic or electrical circuitry to overenergize the valve but the closing time of the valve means remains relatively slow due to the energy stored in the electromagnetic field. It is, therefore, an object of the present invention to provide an electrical means of providing rapid dissipation of the energy stored in the electromagnetic field of the injector valve means.

The general problem described hereinabove has previously been recognized and partially solved, but the solutions proposed have been impractical from the standpoint of repeatability, size and cost. The previous solutions have proposed that an electrical oscillatory circuit be coupled with each independently actuated injector valve means to provide for more rapid dissipation of electrical energy. However, where such circuits are employed, it has been found that the commercially available capacitors, which may be combined with resistors and/or inductors to constitute the oscillatory circuit, will vary from their nominal value sufficiently during their operational life to render the valve closing time, and hence the quantity of fuel injected, indeterminate. This has the end result of causing uncontrolled variations in the amount of fuel delivered to the associated engine. Furthermore, in fuel systems having two or more independently actuated injector valve means, it is possible to have slightly dissimilar valve closing characteristics between each independently actuated injector valve means and thus have fuel mixtures (and operational characteristics) will vary from one injector valve means to the next. This results in rough, uneven engine operation. It is, therefore, an object of the present invention to provide a circuit means for dissipating energy stored in an electromagnetic-field and which is substantially more uniform in commercially available units and quantities. It is a further object of the present invention to provide such a circuit means which is more stable over its operational lifetime. It has further been observed that a plurality of the above-enumerated oscillatory circuits are not readily tunable so it becomes a further object of the present invention to provide a circuit means having the above-enumerated advantages and which may handle more than one independently actuated electromechanical injector valve means to provide unifonnity and repeatability of operation. It is also an object of the present invention to provide a circuit means for dissipating stored electromagnetic energy which is less expensive than previous circuits and which is more electrically uniform from unit to unit. In order to provide a lower cost circuit it is still a further object of the present invention to provide a circuit capable of immediate repeat usage so as to provide a single circuit means capable of dissipating electrical energy stored in a plurality of electromagnetic coil means which are sequentially deactivated.

SUMMARY OF THE PRESENT INVENTION The present invention contemplates a'plurality of diode means interconnecting the independently actuated electromagnetic injector valve means, the diode means having one of their commonly designated electrodes connected together and arranged to prevent current flow from one of said injector valve means to another, and zener diode means coupled to said plurality of diode means by its commonly designated electrode and to the ground or common potential by its other electrode. The polarity of the zener diode means is arranged so that it will conduct (i.e., be biased beyond its reverse voltage breakdown point) by the voltage induced by current flowing through the electromagnetic coils of the injector valve means as a result of the electromagnetic field trying to sustain itself after termination of the control pulse. The zener diode means is selected so that the breakdown point is at a voltage sufficiently low so that the energy stored in the coil of the injector valve means will be substantially dissipated during the zener conduction period.

BRIEF DESCRIPTION OFTHE DRAWING FIG. I shows a schematic diagram of an electronic fuel control system adapted to a reciprocating-piston internal combustion engine.

FIG. 2 shows, in diagrammatic circuit form. an electronic fuel control main computing circuit.

FIG. 3 shows in diagrammatic circuit form the electromagnetic injector valve means and signal amplification stages, adapted to be controlled by the computing circuit of FIG. 2 and including the electronic energy dissipating control mean according to the present invention.

FIG. 4 shows in a series of graphs representativeof selected signal levels present in the electronic fuel control system during a cycle of operation and including graphs representative of injector valve open time.

FIG. 5 shows an enlarged graph of injector valve opening as a function of time.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, an electronic fuel control system is shown in schematic form. The system is comprised of a computing means 10, a manifold pressure sensor 12, a temperature sensor I4, an input timing means 16 and various other sensors denoted as 18. The manifold pressure sensor 12 and the associated other sensors 18 are mounted on throttle body 20. The output of the computing means 10 is coupled to an electromagnetic injector valve member 22 mounted in intake manifold 24 and arranged to provide fuel from tank 26 via pumping means 28 and suitable-fuel conduits 30 for delivery to a combustion cylinder 32 of an internal combustion engine otherwise not shown. While the injector valve member 22 is illustrated as delivering a spray of fuel towards an open intake valve 34, it will be understood that this representation is merely illustrative and that other delivery arrangements are known and utilized. Furthermore, it is well-known in the art of electronic fuel control systems that computing means 10 may control an injector valve means comprised of one or more injector valve members 22 arranged to be actuated singly or in groups of varying numbers in a sequential fashion as well as simultaneously. The computing means is shown here as energized by battery 36 which could be a vehicle battery or a separate battery.

Referring now to FIGS. 1 and 2 and particularly to FIG. 2, an electronic fuel control system main computation circuit 110 is shown. The circuit is shown as being energized by a voltage supply designated as B+ at the various locations noted. In the application of this system to an automotive engine fuel control system, the voltage supply could be a battery 36 and/or battery charging system conventionally used as the vehicle's electric power source. The man skilled in the art will recognize that the electrical polarity of the voltage supply could readily be reversed.

The circuit 1 receives, along with the voltage supply, various sensory inputs, in the form of voltage signals in this instance, indicative of various operating parameters of the associated engine. Intake manifold pressure sensor 12 supplies a voltage indicative of manifold pressure, temperature sensor 14 is operative to vary the voltage across the parallel resistance associated therewith to provide a voltage signal indicative of engine temperature and voltage signals indicative of engine speed are received from input timing means 16 at circuit input port 1 16. This signal may be derived from any source indicative of engine crank angle, but is preferably from the engine's ignition distributor.

The circuit 1 10 is operative to provide two consecutive pulses, of variable duration, through sequential networks to circuit location 118 to thereby control the on time of transistor 120. The first pulse is provided via resistor 122 from that portion of circuit 110 having inputs indicative of engine crank angle and intake manifold pressure. The termination of this pulse initiates a second pulse which is provided via resistor 124 from that portion of the circuit 110 having an input from the temperature sensor 14. These pulses, received sequentially at circuit location 118, serve to turn transistor 120 on (that is, transistor 120 is triggered into the conduction state) and a relatively low voltage signal is present at circuit output port 126. This port may be connected, through suitable inverters and/or amplifiers to the injector valve means (shown in FIG. 3) such that the selected injector valve means are energized whenever the transistor 120 is on. It is the current practice to use switching means to control which of the injector valve means are coupled to circuit location 126 when the system is used for actuation of less than all injector valve means at any one time. Because the injector valve means are relatively slow acting,'compared with the speed of electronic devices, the successive pulses at circuit point 118 will result in the injector valve means remaining open until after the termination of the second pulse.

The duration of the first pulse is controlled by the monostable multivibrator network associated with transistors 128 and 130. The presence of a pulse received via input port 116 will trigger the multivibrator into its unstable state with transistor 128 in the conducting state and transistor 130 blocked (or in the nonconducting state). The period of time during which transistor 128 is conducting will be controlled by the voltage signal from manifold pressure sensor 12. Conduction of transistor 128 will cause the collector 128cthereof to assume a relatively low voltage close to the ground or common volt age. This low voltage will cause the base 134b of transistor 134 to assume a low voltage below that required for transistor 134 to be triggered into the conduction state, thus causing transistor 134 to be turned off. The voltage at the collector 1340 will, therefore, rise toward the B+ value and will be communicated via resistor 122 to circuit location 118 where it will trigger transistor 120 into the on" or conduction state thus imposing a relatively low voltage at circuit port 126. As hereinbefore stated, the presence of a low voltage signal at circuit port 126 will cause the selected injector valve means to open. When the voltage signal from the manifold pressure sensor 12 has decayed to the value necessary for the multivibrator to relax or return to its stable condition, transistor will be triggered on and transistor 128 will be turned off." This will, in turn, cause transistor 134 to turn on," transistor 120 to turn off and thereby remove the injector control signal from circuit port 126.

During the period of time that transistor 134 has been held in the nonconducting, or off state, the relatively high voltage at collector 1341 has been applied to the base of transistor 136, triggering the transistor 136 on." The resistor network 138, connected to the .voltage supply, acts with transistor 136 as a current source and current flows through the conducting transistor 136 and begins to charge capacitor 140. Simultaneously, transistor 142 has been biased on and, with the resistor network 144, constitutes a second current source. Currents from both sources flow into the base of transistor 146 thereby holding this transistor on" which results in a low voltage at the collector 1460. This low voltage is communicated to the base of transistor 120 via resistor 124.

When transistor 128 turns "off" signalling termination of the first pulse, transistor 134 turns on" and the potential at the collector 134a falls to a low value. The current from the current source, comprised of transistor 136 and resistor network 138, now flows throughthe base of transistor 136 and the capacitor 140 ceases to charge. The capacitor will then have been charged, with the polarity shown in FIG. 2, to a value representative of the-duration of the first pulse. However, at the end of the first pulse when transistor 134 is turned on," the collector-base junction of transistor 136 is forward biased, thus making the positive side of capacitor 140 only slightly positive with respect to ground as a result of being separated from ground by only a few PN junctions. This will impose a negative voltage on circuit location 148 which will reverse bias diode and transistor 146 will be turned off." This will initiate'a high voltage signal from the collector of transistor 146 to circuit location 118 via resistor 124 which signal will re-trigger transistor 120 on" and a' second injector means control pulse will appear at circuit port 126. The time duration between the first and second pulses will sufficientlyshort so that the injector means will not respond to the brief lack ofsignal.

While the diode 150 is reverse biased, the current from the current source comprised of transistor 142 and resistor network 144 will be flowing through circuit location 148 and into the capacitor 140 to charge the capacitor to the point that circuit location 148 will. again be positive. This will then forward bias diode 150 and transistor 146 will turn back on. This will terminate the second pulse and the injector valve means, not shown, will subsequently close.

The duration of the second pulse will be a function of the time required for circuit location 148 to become sufiiciently positive for diode 150 to be forward biased. This in turn is a function of the charge on capacitor 140 and the magnitude of the charging current supplied by the current source comprised of transistor 142 and resistor network 144. The charge on capacitor 140 is, of course, a function of the duration of the first pulse. However, the rate of charge (i.e., magnitude of the charging current) is a function of the base voltage at transistor 142. This value is controlled by the voltage divider networks 152 and 154 with the effect of network 154 being variably controlled by the engine temperature sensor 14. I

Referring now to-FIGS. 2 and 3 and particularly to FIG. 3, the present invention is illustrated as applied to the injector valve means control stages. FIG. 3 shows two intercoupled substantially identical circuits 200 and 202 which are adapted to selectively control energization of the first and second electromagnetic means 204 and 206. A portion of the electromagnetic means may comprise the energizing means for injector valve means 22. As shown here each electromagnetic means in the actuating sequence comprises a plurality of electromagnetic coil members. Circuits 200 and 202 also include input means from circuit port 126 of FIG. 2, an electromagnetic coil means selector means 208, and power amplifier means 210 and 211.

interconnecting the electromagnetic means 204 and 206 are a diode means comprised of a pair of diode members 212 and 214. These diode members are arranged in a one-to-one relationship witheach electromagnetic means 204 and 206, and are connected thereto by a commonly designated electrode, in this case the cathode. Thus, the diodes are arranged to block current flow from the power amplifier means 210 and 211. The diodes are additionally interconnected by their other electrodes (i.e., their anodes in this instance) to provide a circuit point 215 to which current from the amplifiers 210 and 211 is prevented from flowing. A zener diode member 216 is also included in the diode means and is connected to circuit point 215 by its electrode corresponding in designation to the other diode means electrodes connected thereto.

The power amplifier means 210 and 211 are comprisedof a plurality of transistors 218, 220, 222, 224 and resistors 226, 228, 230, 232 and are operative to provide substantially square voltage waveforms, at approximately the voltage level of the supply, to the various electromagnetic means 204 and 206. Thus, a relatively low strength signal at circuit port 126 will produce a substantially identical signal for the selected coil means having, however, a higher maximum voltage.

With reference to FIGS. 2, 3 and 4, the operation of the circuit is as follows: The circuit of FIG. 3 will receive, at input port 126, electrical signals from the main computing circuit 110 as illustrated by graphs A and B in FIG. 4. The graph B pulses will immediately follow the graph A pulses and these signals will be applied to the inputs of the power amplifier 210 and 211 at the bases of transistors 218 as illustrated by graph E. It should be pointed out at this juncture that, while the graphs A, B, C, D and E represent positive signal waveforms, the specific signals illustrated will be at the common or ground potential since the specific embodiment illustrated herein is one in which a voltage approaching the supply voltage is treated as a lack of signal. Selector means 208, which may be, for instance, a bi-stable flip flop selectively triggered by a means indicative of engine crank angle such as timing pick-up 16, will apply a signal to power amplifier 210 in accord with graph C and to power amplifier 211 in accordance with graph D. The time period denoted as T on the graphs of FIG. 4 thus represents one cycle of operation for circuit 110 (of FIG. 2) and, in the present embodiment which shows two independently actuated injector valve means actuated by electromagnetic means, one-half of a complete cycle of the FIG. 3 circuit, or one revolution of the engine crank shaft. While the signals from the main computing circuit 110 are applied to each power amplifier 210 and 211, the signal from the selector means 208 is applied to only one power amplifier 210 or 211. The only power amplifier which will respond is the power amplifier which receives signals from both main computing circuit 110 and selector means 208. For the purposes of the remainder of this description, it will be assumed that the signal represented by graph C is applied to power amplifier 210. This will produce a voltage drop across the collector-base junction of transistor 220 and transistor 220 will become conducting. This will cause a voltage differential to appear across the emitter-base junction of transistor 222. This, in turn, will apply a voltage to the base of transistor 224 driving it into conduction and the supply voltage will be applied, virtually undiminished, to the coil means 204. Diode 212 will block current flow through the connecting branch while current flows through the electromagnetic means 204. As the current begins to build up in the electromagnetic coils of electromagnetic means 204, the injector valve means associated therewith will begin to open in accord with graph F of FIG. 4. Upon termination of the graph E signal, the transistors 218, 220, 222, 224 will become nonconducting and the supply voltage will be removedfrom the injector valve means associated with electromagnetic means 204. Due to the inductances of the electromagnetic coils, and the energy stored in the electromagnetic fields thereof, current fiowthrough the electromagnetic means will not immediately cease but will tend to continue to flow. Since transistor 224 is not conducting, this induced cur rent will be drawn through diode 212 in the forward direction and zener diode 216 in the reverse direction. The induced current will be produced by the induced voltage at the electromagnetic means 204 which voltage will be of a polarity opposite to that of the injector valve opening current and the magnitude of this voltage will be sufficient to cause zener diode 216 to break down. The energy stored in the electromagnetic fields will be dissipated bythe zener diode 216 and the various circuit resistances present in theelectromagnetic coils of electromagnetic means 204. Thus, a current flow path and energy dissipating means are provided to hasten the closing of the injector valve means 22.

During the next cycle of operation, electromagnetic means 206 will be energized in substantially the same manner as described hereinabove with regard to injector valve means 204. Termination of the second pulse shown in graph B will cause transistor 224 in power amplifier 211 to become nonconducting and electromagnetic means 206 will cease to be energized. An induced current will be drawn in through diode 214 (now forward biased) and through the zener diode 216, providing a current flow path to rapidly and reliably dissipate energy stored in the electromagnetic fields associated with the inductances of the electromagnetic means 206.

With reference to FIG. 5, the improved injector valve means closing time is illustrated in graphical form. The graph represents an enlargement of the graph F waveform from FIG. 4. The waveform is shown with two trailing edges, identified as edge 300 and edge 301. This graph illustrates valve opening as a function of time, t, and the edge 300 is representative of the closing time achieved by practical oscillatory circuitry and the edge 301 is representative of the closing time achieved by a practical version of the present invention. By practical is meant an arrangement of elementsof commercial availability and sized so as to operate in an electronic fuel control system for internal combustion engines.

As will be apparent to the man of ordinary skill in the art, zener diode means 216 could actually be a pair of zener diodes one of which would be connected to diode 212 and the other of which would be connected to diode 214. In such an arrangement, diodes 212 and 214 could be electrically interconnected as shown or they could be electrically independent.

While a plurality of zener diodes could be used, and such usage would provide a less expensive, more reliable and uniform rate of controlled energy release from the injector valve means than is obtained by the prior art circuit means, additional advantages are observed in a system using a plurality of sequentially actuated injector valve means. Whereas prior art means of assisting energy release from the electromagnetic fields associated with electromechanical fuel injector valves required an inactive period to release stored energy, the zener diode means disclosed herein may be repeatively used without a mandatory inactive period. Therefore, a single zener diode will suffice for any number of sequentially activated injector valve means.

I claim: I

1. An electronically controlled fuel supply system for internal combustion engines having electromagnetically actuable injector valve means for controlling delivery of fuel to the engine comprising:

electromagnetic means operative to produce electromagnetic fields for actuating the injector valve means; computing means for generating a signal indicative of the engine demand for fuel;

control means intercommunicating said computing means and said electromagnetic means responsive to said computing means signal for controllably energizing said electromagnetic means;

diode means electrically connected to said electromagnetic means in shunt relation operative to be reverse biased when said electromagnetic means are energized by said control means; the injector valve means comprising a plurality of sequentially actuable electromagnetically actuated injector valve members and said diode means comprising a plusaid diode means responsive to induced current flow in said electromagnetic means following termination of said energization to be biased beyond the zener breakdown point, thereby providing a rapid discharge path for energy stored in the electromagnetic fields of said electromagnetic means.

2. The system as claimed in claim 1 wherein said plurality of diodes is at least equal in number to the number of said elec- 1O tromagnetic means in the actuating sequence. 

1. An electronically controlled fuel supply system for internal combustion engines having electromagnetically actuable injector valve means for controlling delivery of fuel to the engine comprising: electromagnetic means operative to produce electromagnetic fields for actuating the injector valve means; computing means for generating a signal indicative of the engine demand for fuel; control means intercommunicating said computing means and said electromagnetic means responsive to said computing means signal for controllably energizing said electromagnetic means; diode means electrically connected to said electromagnetic means in shunt relation operative to be reverse biased when said electromagnetic means are energized by said control means; the injector valve means comprising a plurality of sequentially actuable electromagnetically actuated injector valve members and said diode means comprising a plurality of diode members, each having a pair of electrodes, interconnecting said electromagnetic means and connected thereto by a commonly designated electrode whereby current flow from said control means to said electromagnetic means is prevented from flowing through said diode members; the other of the diode member electrodes connected together at a common circuit point; and a zener diode member, having two electrodes, connected to said other electrodes by its electrode which bears the same designation as said other electrodes; said diode means responsive to induced current flow in said electromagnetic means following termination of said energization to be biased beyond the zener breakdown point, thereby providing a rapid discharge path for energy stored in the electromagnetic fields of said electromagnetic means.
 2. The system as claimed in claim 1 wherein said plurality of diodes is at least equal in number to the number of said electromagnetic means in the actuating sequence. 